One purpose for developing a permanently implanted total artificial heart would be to replace a diseased, failing heart that would in the immediate future cause the patient's demise. Another use for an artificial heart is as a temporary blood pump to keep a patient alive while awaiting a suitable donor transplant heart. Another use would be to use it externally as equipment to pump blood during open heart surgery or during hemodialysis.
Gas energized artificial hearts have been used and do well as temporary blood pumps to fill the hiatus between total failure of the natural heart and a suitable allograph transplant. However, gas energized systems are unsuitable for permanent replacement because the gas cannot be contained in the closed system for prolonged periods of time. Turbine powered hydraulic pumps that have been used for pumping blood are of two types. The Jarvik pump uses a reversible brushless motor that goes from about 10,000 rpm in one direction to 10,000 rpm in the opposite direction in a period of 25 milliseconds which in some instances have caused bearing failures. The other type is the "Turbo-Pulsatile Total Replacement Artificial Heart" which uses a turbine that rotates in only one direction but has a valving system that shunts the hydraulic fluid between the right and left pumping chambers. This system is more difficult to install and takes up more space than the natural heart. It would be more desirable to replace the natural heart with an artificial heart in an orthotopic position.
The present invention is directed towards an axial thrust powered hydraulic pump in which the pitch angle of the impeller blades changes to cause the hydraulic fluid to flow in a reverse direction without changing the direction of the blades. That is, the blades rotate continuously and always rotate in the same direction, but the pitch angle of the blades is alternately reversed to provide the pulsed pumping cycle.